A technique has been developed for electrophysiological recording from single brain neurons during experimentally-induced epileptic seizures in the rat. During the reporting period, studies were carried out on norepinephrine (NE)-containing neurons in the locus coeruleus. Central NE neurons have been implicated in the regulation of seizure activity in several animal seizure models. The experiments were designed (1) to determine how NE neurons respond during seizures so as to better understand their modulatory role and (2) to understand the changes occurring in CNS NE systems as a result of seizures. Distinctive changes in the firing activity of locus coeruleus NE neurons wee observed with chemically (pentylenetetrazol) and electrically (electroshock) induced seizures. Both treatments induced intense firing in the periictal period with depression of firing or bursting in snychrony with cortical spiking after the major seizure discharge. These studies help to explain biochemical changes occurring in human epileptic brain, provide further understanding of the mechanism of action of electroconvulsive therapy in depression, and provide a basis for attempts to control seizures with adrenergic drugs.